The first wave of amass cards all created a Zombie Army, but with the addition of amass orcs in LTR, the original mechanic was changed to amass zombies. This allows different sets to represent armies that match the flavor of that set
It also serves to advertise Pokemon to a larger audience, which is a net good for the hobby in the long run
Stony Silence is played more, and its $5
Theres also nothing saying you cant target your own creatures, which makes this yet another cool piece for Stuffy Doll to play with
Lapras ex, with its massive health pool and an attack that both deals big damage to opposing Pokmon and heals itself, is the obvious highlight of the promotional series
Still, its a very cool card with excellent composition